Heating unit and method of making it



Jan. 8, 1929.

C. C. ABBOTT HEATING UNIT AND METHOD OF MAKING IT Filed Nov. 18, 1924 Inventor @J. m w M H Patented Jan. 8, 1929.

UNITED STATES 1,698,289 PATENT OFFICE.-

GEABLIS C. ABBOTT, PITTSFIEID, MASSACHUSETTS, ABBIGNOB TO GENERAL mo- TBIG COIPANY, A CORPORATION OF NEW YORK.

m'rmo mm. AND IETEOD or name rr.

. Application filed November 18, 1924. Serial No. 750,666.

My invention relates to electric heating units and has for its object the provlsion of an improved support and insulator for the terminals of heating units. I

More particularly, my invent1on relates to heating units of the cartridge type and especially to such units which are compactedby reducing their size, for example, by swagmg or rolling. Such a heating unit 15 described and claimed in my Patent No. 1,432,434, dated October 17, 1922. In heating units of this type it is desirable to use a solid insulator for the terminals which is so arranged that it is not crushed and thereby destroyed by the compacting operation. 0

In carrymg out my invention provide a support and insulator for the terminals of the heating unit which is secured in a port on of the heating unit which is of smaller size so that the insulator is not injured by the reducing procem by means of which the unit is compacted. I

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is an ele vation view in section showing the assembly of the various parts of a heating unit embodying my invention; Fig. 2 is a plan view of Fig. 1; while Fig. 3 is an elevation view partially in section of the completed unit shown in Figs. 1 and 2.

Referring to the drawing, in one form of my invention, the heating unit comprises an outer metallic cylindrical sheath 10 having an enlarged body portion 11 and a shorter portion 12 of smaller diameter at one end. The resistance heating conductor wire 13 is wound on a cylindrical core or support 14 made of suitable insulating material, such as lava. Apertures or recesses 15 and 16 are provided in one end of the core 14 for the terminal members 17 and 18. These apertures extend parallel with the length of the core. Agroove or slot 21 is formed in the core on the same side as recess 16 and extending the full length of the core. This slot is deep enough to cut into recess 16. A slot 22 extends across the end of the core opposite the recesses 15 and 16, and a longitudinally extending slot 19 substantially the length of recess 15 is formed cutting into recess 15. The depth and width of slots 19, 21 and 22 is somewhat greater than the diameter of the resistance conductor 13.

Theresistance conductor is wound in the member, and the terminal member given two form of a helix on the core with its turns spaced apart at suitable intervals so that the may be insulated from each other. In win ing the resistance conductor on the core, the terminal member 18 is inserted-in the aperture 16 and turned so that a lateral hole 23 through it is in alignment with slot 21. The end of the resistance conductor is then inserted through the hole 23 in the terminal or three complete turns, or more, so as to wind the resistance conductor on it, the turns of the resistance conductor being bound securely between the terminal member and the wall of recess 16. This forms a good electrical and also mechanical connection. The resistance conductor is then laid in a longitudinal groove 24 in the terminal member, the terminal member rotated through a half revolution to the position shown in the drawing, and the resistance conductor then laid in the slot 21 and brought across the end of the core in slot 22. It is then wound in helical form on the core toward the opposite end and when the core has been covered with turns or a sufficient number have been wound on to give the desired amount of resistance, the resistance conductor is cut ofi so as to leave a free end of such length that it may be inserted in a lateral aperture 25 in terminal member 17. The terminal member 17 is then given several complete turns to wind up the resistance conductor tightly on the core and also establish a good electrical and mechanical connection between the resistance conductor and the terminal member.

After the resistance conductor and ter minal members have thus been asembled on the core, a washer 26 of suitable insulating material, such as mica, is placed over the pro- 5 jecting ends of the terminal members, the washer being provided with apertures suitably spaced to receive the terminal members.

As shown, the projecting ends of the terminal members may be somewhat smaller than the port-ions inserted in the core so that the washer 26 rests against shoulders on the terminal members. A terminal support and insulator 27,- made of porcelain or the like having suitably spaced apertures 28 and 29 to receive the ends of the terminal members is then put in place and seated on the washer 26. This insulator 27 is smaller in diameter than the bod portion 11 and is of such size as to fit loosely in the portion 12.

The assembled parts previously described I are next inserted in the sheath 10, thg' terminal ends being inserted first so that the insulator 27 is seated in the portion 12. As shown the end of the portion 12 may be spun over at 30 to secure the insulator, the insulator having a corresponding bevelled portion 31. A smaller portion 32 is preferably provided on the insulator 27 so as to proiect for a short distance from the sheath. 'lhis construction of the insulator 27 permits the terminals, the outer ends of which maybe stranded so as to be flexible, to be bent at sharp angles outward without coming into contact with the metallic sheath.

A filling member 35 is then inserted in the open end of the sheath. This filling member is provided with spaced projections 36 arranged in a circle and fitting between the turns of the conductor and the inside of the sheath so as to hold this end of the core centrally of the sheath. The other end of the core is held centrallyby means of the terminals which are seated in the apertures in the insulator 27. The filling member 35 is in the form of a cup or container, the projections 36 being secured to the bottom. It is also provided with apertures 37 in the bottom which may be and preferably are placed between the projections 36. Suitable granulated or powdered insulating material 38, such as magnesia, is next put in the filling member 35 and shook down through the apertures 37 into the sheath. During this filling operation the unit is held in an upright position, as shown in Fig. l of the drawing, and is preferably placed in a suitable vibrating machine whereby it is jarred or vibrated rapidly and the insulating material 38 shook down in ductivity.

the sheath around the resistance conductor and between its turns. The vibrating action shakes the particles of the insulating material together and compacts them to a considerable extent. The insulating material also fills the slots 19, 21 and 22 and the recesses 15 and 16 around the terminal members. A metallic disc or cap 39 is then. inserted to close the sheath and the end spun over at 40 to secure the cap in place.

In the final operation the diameter of the body portion 11 is reduced so as to thoroughly compact the powdered insulating material into a hard dense mass having excellent insulating properties and also good heat conhis reducing and compacting operation is preferably done by passing the unit through a suitable swaging machine. It may, however, be accomplished by rolling. During this compacting, the lava of the core may be caused to flow somewhat, and the insulating material in the recesses 15 and 16 is compacted around the terminal members so as to secure them in place. The reduction in diameter of the body portion 11 during the compacting operation is less than the diiferneeaaee euce between the diameters of the body port ion 11 and the end portion 12. The swaging machine, therefore, does not. come in contact with the portion 12 and the insulator 27 is therefore not reduced in diameter. As shown in Fig. 3, after the unit has been swaged the body portion is still somewhat larger than the portion 12.

, While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. An electric heating unit comprising a metallic sheath reduced in diameter to compact the unit core of insulating material, a resistance conductor wound on said core, powdered heat refractory insulating material in said sheath compacted around said resistance conductor, a portion of said sheath of smaller diameter at one end, an insulator secured in said end portion provided with apertures, and terminals for said resistance conductor extending through said apertures.

2. An electric heating unit comprising a core of insulating material, a resistance conductor wound on said core, a metallic sheath surrounding said resistance conductor and core, powdered heat refractory insulating material compacted to a hard dense mass between.

said resistance conductor and sheath, said sheath being reduced in diameter to compact said insulating material, a cylindrical portion of smaller diameter at one end of said sheath, and an insulator and support for the terminals of said resistance conductor secured in said cylindrical reduced portion.

3. The method of making an electric heating unit which consists in providing a tubular metallic sheath having an enlarged body portion and a smaller portion at one end, inserting an insulator in said smaller portion, mount-ing a resistance conductor in the body portion and bringing its terminals out through said insulator, and then compacting the unit by reducing the body portion of said sheath an amount less than the diflerence between the transverse sectional dimensions of said body and said end portions.

4. The method of making an electric heating unit which consists in providing a metallic sheath having an enlarged body portion and a portion at one end of lesser diameter, inserting an insulator in said smaller portion. mounting a resistance conductor in said body portion and bringing its terminals out through said insulator, filling said body portion with a powdered heat refractory insulating material, and then reducing the body porin securing an insulator in a portion of said tion to compact said insulating material to a sheath of reduced size, and then compacting hard dense mass around said resistance conthe unit by reducing the diameter of the re doctor. the transverse sectional dimensions of maining portion of said sheath by an amount said body portion being greater after the re less than the difference in diameter of said 15 ducing operation than the transverse secportions.

tional dimension of said smaller end por- In witness whereof,Ihave hereu tion.

5. The steps in the method of making a 10 sheathed electric heating unit which consist CHARLES C. ABBOTT.

nto set my hand this 14th day of November, 1924. 

